When stock-removal waste, such as turnings or the like, is comminuted, the possibility of large-sized parts, such as end pieces for example, also passing into the comminuting device cannot be ruled out in practice. These parts are in many cases so hard or solid that they cannot be comminuted by the knives, so that the comminuting device is overloaded. In this event, the overload protection responds and the machine stops. The switching-on of a reversing mechanism then causes the shafts, including the knives, to be rotated in the opposite direction so that the part is moved from the working gap of the knives to the top and to the side. When the machine is switched on again, the part now passes again into the knife working gap and, if it is of sufficient strength, once more causes a machine stoppage involving an overload switch-off. This process is repeated until the part has been removed from the comminuting device, so that considerable impairments of the waste comminution are caused. Another disadvantage consists in the fact that a repeated machine blockage by the same part increases the wear of the knives.